Patent application title: SYSTEM AND METHOD FOR A MICRO RING LASER

Abstract:

A system and method for an electrically pumped laser system is disclosed.
The system includes a silicon micro-ring resonator 405. A quantum well
412 formed of a III-V group semiconductor material is optically coupled
with the micro-ring resonator 405 to provide optical gain. A trapezoidal
shaped buffer 414 formed of a III-V group semiconductor material and
doped with a first type of carrier is optically coupled to the quantum
well 412. A ring electrode 410 is coupled to the trapezoidal shaped
buffer 414. The trapezoidal shaped buffer 414 enables the ring electrode
410 to be substantially isolated from an optical mode of the micro-ring
resonator 405.

Claims:

1. An electrically pumped hybrid III-V group and silicon laser system,
comprising:a silicon micro-ring resonator 405;a quantum 412 well formed
of a III-V group semiconductor material that is optically coupled with
the silicon micro-ring resonator 405 to provide optical gain;a
trapezoidal shaped buffer 414 formed of a III-V group semiconductor
material doped with a first type of carrier, wherein the trapezoidal
shaped buffer 414 is optically coupled to the quantum well 412;a ring
electrode 410 coupled to the trapezoidal shaped buffer 414, wherein the
trapezoidal shaped buffer 414 enables the ring electrode 410 to be
substantially isolated from an optical mode of the micro-ring resonator
405.

2. The system of claim 1, further comprising a second buffer 408 formed of
III-V group semiconductor material doped with a second type of carrier
having a charge opposite the first type of carrier, the second buffer 408
being located between the quantum well 412 and the silicon micro-ring
resonator 405.

3. The system of claim 2, wherein a height of the silicon micro-ring
resonator 405, the second buffer 408, the quantum well 412, and the
trapezoidal shaped buffer 414 is selected to enable a single fundamental
transverse-electric (TE) mode of laser light to propagate within the
resonator 405, with a maximum amount of electromagnetic energy in the
TE-mode located within the quantum well 412 to provide increased
amplification of laser light within the quantum well 412.

4. The system of claim 2, further comprising a center electrode 416
coupled to the second buffer 408 and located inside the silicon
micro-ring resonator 405 to allow carriers to be injected into the
quantum well 412 by applying a bias potential between the center
electrode 416 and the ring electrode 405.

5. The system of claim 1, wherein the trapezoidal shaped buffer 414 is
comprised of a plurality of levels, with each increasing level having a
decreasing length to form a pyramidal shaped buffer.

6. The system of claim 5, wherein the pyramidal shaped buffer is formed by
etching a plurality of steps to form the plurality of levels.

7. The system of claim 1, further comprising an under-cladding layer 404
located below the silicon micro-ring resonator 405, wherein the
under-cladding layer 404 is formed of a material having an index of
refraction that is less than the index of refraction of the silicon
micro-ring resonator 405 and that is substantially optically transparent
at a wavelength of laser light within the micro-ring resonator 405.

8. The system of claim 1, further comprising an optical waveguide 302
located sufficiently close to the silicon micro-ring resonator 405 to
enable laser light from the micro-ring resonator 405 to couple
evanescently to the optical waveguide 302.

9. A method for forming an electrically pumped hybrid III-V group and
silicon laser for stimulating light of a selected wavelength,
comprising:forming a silicon micro-ring resonator 405 on an
under-cladding 404 having an index of refraction that is less than an
index of refraction of the silicon micro-ring resonator 405;joining a
first buffer layer 408 with the silicon micro-ring resonator 405, wherein
the first buffer layer 408 is formed of a III-V group semiconductor
material doped with a first type of carrier;attaching a quantum well 412
to the first buffer layer 408, with the quantum well being optically
coupled to the silicon micro-ring resonator 405;connecting a second
buffer layer 414 to the quantum well 412, wherein the second buffer layer
414 is formed of III-V group semiconductor material doped with a second
type of carrier having a charge opposite the first type of carrier and
the second buffer layer 414 has a trapezoidal shape having a wide area
coupled to the quantum well 412 and a narrow area;joining a ring
electrode 410 to the narrow area of the trapezoidal shaped second buffer
layer 414; andincluding a center electrode 416 near a center of the
silicon micro-ring resonator 405 to enable carriers to be injected into
the quantum well 412 between the center electrode 416 and the ring
electrode 410 to provide amplification of the light of the selected
wavelength.

10. A method as in claim 9, further comprising forming the trapezoidal
shape of the second buffer layer 414 by etching a plurality of levels,
with each increasing level having a decreasing length to form a pyramidal
shaped buffer.

11. A method as in claim 9, further comprising forming the trapezoidal
shape of the second buffer layer 414 shaped with a narrowed top portion
to direct a single fundamental TE-mode such that the maximum amount of
electromagnetic energy in the single fundamental TE-mode is located
within the quantum well 412 to provide increased gain of the light within
the quantum well 412.

12. A method as in claim 9, further comprising positioning an optical
waveguide 302 sufficiently close to the silicon micro-ring resonator 405
to enable the light within the silicon micro-ring resonator 405 to
evanescently couple to the optical waveguide 302 to enable laser light to
be directed from the silicon micro-ring resonator 405.

13. An electrically pumped hybrid III-V group and silicon laser system,
comprising:a silicon micro-ring resonator 105;a quantum well 112 formed
of a III-V group semiconductor material that is optically coupled with
the silicon micro-ring resonator 105 to provide optical gain;a first
buffer 114 formed of a III-V group semiconductor material doped with a
first type of carrier, wherein the first buffer 114 is coupled to the
quantum well 112;a second buffer 108 formed of a III-V group
semiconductor material doped with a second type of carrier, wherein the
second buffer 108 is located between the quantum well 112 and the silicon
micro-ring resonator 105;a center electrode 116 located at a center of
the silicon micro-ring resonator 105 and coupled to the first buffer 114,
wherein the first buffer 114 enables the center electrode 116 to be
substantially isolated from an optical mode of the micro-ring resonator
105.

14. The system of claim 13, further comprising an outer electrode 110
coupled to the second buffer 108 and located a selected distance from the
micro-ring resonator 105.

15. The system of claim 13, further comprising an optical waveguide 302
located sufficiently close to the silicon micro-ring resonator 105 to
enable laser light from the micro-ring resonator 105 to couple
evanescently to the optical waveguide 302.

Description:

BACKGROUND

[0001]As computing power and data storage capacities have exponentially
increased over the last several decades, a corresponding amount of stored
data has also exponentially increased. Computers which were once the
domain of text files and a few low resolution pictures are now often used
to store thousands of high resolution pictures and hours of video.
Television sets are being upgraded to show high definition video. New
generations of optical discs have been developed to hold the high
definition video. The discs can hold as much as 50 gigabytes of data on
each side. This is enough to store several hours of video in a high
definition format. Ever denser storage formats are being developed to
store the increasing amounts of information.

[0002]Moving and transmitting the vast amounts of digital information is
becoming more challenging. Each year, more electronic devices are
available that can digitally communicate with other devices. Electronics
including computers, high definition television, high definition radio,
digital music players, portable computers, and many other types of
devices have been designed to transmit and receive large amounts of
information. Many computers now receive broadband internet which is
broadcast throughout the home. Televisions are receiving multiple high
definition signals from cable and fiber optics.

[0003]In order to transmit the immense quantities of data stored in
computers and broadcast to televisions and other electronics devices, the
data is transmitted at ever faster rates. However, transmission rates are
not keeping up with the explosion in data. For example, to transmit a
typical 15 gigabyte high definition movie from an optical disk to a home
entertainment system, it requires 100 megabits to be transmitted per
second for twenty minutes. For many users, taking 20 minutes to transfer
a movie can be burdensome.

[0004]Similarly, higher bandwidth communication between processors,
memory, other chips, and computer boards within a computer system is
needed. One way to decrease the amount of time it takes to move large
amounts of digital information between computer chips is to transmit the
information at faster speeds. Transmission speeds that can move large
volumes of data in a reasonable time, however, have historically been too
costly to be broadly used in consumer electronics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 illustrates a cross sectional view of a hybrid III-V-silicon
micro-ring electrically pumped laser system in accordance with an
embodiment of the present invention;

[0006]FIG. 2 illustrates a cross sectional view of a simulated optical
mode using the structure illustrated in FIG. 1 in accordance with an
embodiment of the present invention;

[0007]FIG. 3 illustrates a top view of a micro-ring electrically pumped
laser system evanescently coupled with an optical waveguide in accordance
with an embodiment of the present invention;

[0008]FIG. 4 illustrates a cross sectional view of a micro-ring
electrically pumped laser system having a trapezoidal shaped buffer in
accordance with an embodiment of the present invention;

[0009]FIG. 5 illustrates a cross sectional view of a simulated optical
mode using the structure illustrated in FIG. 4 in accordance with an
embodiment of the present invention; and

[0010]FIG. 6 illustrates a flow chart depicting a method for forming an
electrically pumped laser for stimulating light of a selected wavelength
in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0011]Optoelectronic integration on silicon is a technology used to build
optical interconnection systems and other large-scale photonic systems on
a chip. Integrated photonic systems typically use a lower cost and
easy-to-integrate electrically pumped laser source. Silicon, however, is
limited by its fundamental material properties and therefore cannot
efficiently provide the electrically pumped optical gain used in laser
operation. Therefore, hybrid integration of gain material, such as III-V
group semiconductors located on a silicon platform, can be used to
construct an on-chip electrically pumped laser.

[0012]In order for the integrated electrically pumped laser source to be
marketable, the process of integrating the III-V group gain material onto
the silicon needs to be relatively low cost and easy to implement. In one
embodiment, the present invention provides a system and method for making
a micro-ring resonator that can be used as a relatively small on-chip
laser source that can be directly modulated at speeds greater than one
gigahertz. An electrically pumped laser source using a ring modulator can
be used to send information across a chip and then off-chip to waveguides
and neighboring electronic devices. The electrically pumped laser source
using a ring modulator can be implemented relatively inexpensively since
it relies on wafer-bonding that does not require critical alignment in
the bonding step, as is typically needed in chip-bonding.

[0013]FIG. 1 illustrates a cross sectional view of a hybrid III-V-silicon
micro-ring electrically pumped laser system 100. In this example, a
silicon substrate 102 is illustrated to support the laser system. Other
types of substrates that are used in semiconductor manufacturing
processes are considered to be within the scope of the present invention.
An under-cladding 104 can be formed on the silicon substrate. A silicon
micro-ring resonator 105 can be constructed on the surface of the
under-cladding. The under-cladding is used to substantially constrain
light within the silicon micro-ring resonator.

[0014]The under-cladding can be constructed of a material that has an
index of refraction that is less than the index of refraction of the
silicon micro-ring resonator and is substantially transparent at the
wavelength of light injected in the resonator. For example, the
under-cladding may be formed using silicon dioxide. Alternatively, the
under-cladding may be formed of a material such as silicon nitride or
another material meeting the above requirements. The area within 120 and
outside of 106 the micro-ring resonator can also be formed of a material
that has an index of refraction that is less than the refractive index of
the resonator and is substantially transparent at the wavelength of light
injected in the resonator. In one embodiment, the area within and outside
of the micro-ring resonator can be formed of air or a vacuum.
Alternatively, another substance such as silicon dioxide or silicon
nitride may be used.

[0015]The silicon micro-ring resonator 105 can have a radius that is
roughly proportional to or slightly smaller than a wavelength of the
light that is carried by the micro-ring resonator. Alternatively, the
radius of the silicon micro-ring resonator can be greater than the
wavelength of the light. For example, the wavelength of the light may be
1.54 micrometers and the radius of the micro-ring resonator configured to
carry the light can be about 3 micrometers. Typical dimensions for the
silicon micro-ring resonator can vary from 2.5 microns to tens of microns
depending on the wavelength of the light and other design considerations.
Other wavelengths of light can also be used, such as the 1.31 micron
wavelength commonly used in telecommunications. The silicon micro-ring
resonator can be designed to carry wavelengths of light ranging from the
deep infrared to ultraviolet light.

[0016]A PN junction can be constructed across a quantum well 112 that is
optically coupled with the micro-ring resonator 105. A quantum well is a
potential well that confines carriers, which were originally free to move
in three dimensions, to two dimensions, forcing them to occupy a planar
region. Because of their quasi-two dimensional nature, electrons in
quantum wells have a sharper density of states than bulk materials. The
quantum well structure is used to alter the density of states of the
semiconductor, and results in an improved semiconductor laser requiring
fewer carriers (electrons and holes) to reach laser threshold than other
types of structures such as a conventional double heterostructure. The
quantum well can be comprised of a III-V group material such as such as
indium phosphide, indium gallium arsenide phosphide, and the like. A
single or multiple quantum well may be used in the disclosed embodiments,
as can be appreciated. The quantum well 112 can be wafer bonded to a
buffer layer 108. Wafer bonding the quantum well to the buffer layer can
provide for lower tolerances in manufacturing the device, as previously
discussed.

[0017]The PN junction formed by the two contacts 108, 114 can also be
comprised of a III-V group material, with the material being doped with a
carrier. In one embodiment, an n-doped contact 108 can be directly placed
on the silicon micro-ring resonator 105. Supports 118 can be used to
carry the n-doped contact. The quantum well 112 can be placed on the
n-doped contact and aligned collinearly with the micro-ring resonator to
enable the quantum well to be optically coupled with the micro-ring
resonator. A p-doped contact 114 can be placed on the opposite side of
the quantum well from the n-doped contact to form a PN junction. In one
embodiment, the quantum well can be considered an intrinsic layer. The
p-contact, the n-contact, and the quantum well can then be considered a
PIN junction.

[0018]Electrodes 116 and 110 can be positioned as illustrated in FIG. 1 to
forward bias the PN junction to provide carriers within the quantum well
112. In one embodiment, the electrodes can be formed of a metallic
material. Alternatively, a substantially conductive, non-metallic
material or a composite may be used to inject current into the quantum
well. The center electrode 116 can be coupled to the p-contact 114 and
positioned coaxial with the quantum well and micro-ring resonator 105. A
distance 117 between the outer edge of the center electrode and the inner
edge of the micro-ring resonator may be approximately 0.3 to 1.0
micrometers. An outer electrode 110 can be located outside the micro-ring
resonator. The outer electrode can be separated by a distance 113 of 0.5
to 1.0 micrometers from the quantum well. The combined thickness 115 of
the n-contact 108, the quantum well 112, and the p-contact may be
approximately 0.2 to 0.4 microns. The electrodes can be used to forward
bias the PN junction and inject current into the quantum well. Obviously,
the n and p doped contacts can be switched and the bias reversed to
achieve the same result.

[0019]In prior electrically pumped diode lasers, the electrodes that
contact the semiconductor material have high optical losses. Therefore,
the electrodes are usually isolated from the optical mode of the
resonator. This means that the electrodes have to be placed several
micrometers away from the center of the optical resonator. In the
electrically pumped laser system 100 illustrated in FIG. 1, the quantum
well 112 gain medium is bonded on top of the silicon-based micro-ring
resonator 105.

[0020]Mode isolation from a top electrode typically uses a relatively
thick buffer layer between the quantum well and the center electrode.
This buffer layer has a refractive index close to that of silicon. The
presence of this thick buffer layer can severely limit the ability to
confine light in a micro-ring resonator since the optical mode will
spread into this buffer layer instead of following the tightly bent path
of the micro-ring resonator. Previous attempts to overcome this problem
have included constructing a ring resonator with a perimeter of over 2
millimeters. A ring resonator of this size is quite large to be
integrated in a microchip. Additionally, a large ring resonator typically
cannot be modulated at a sufficiently high speed needed for on and
off-chip communications.

[0021]The structure illustrated in FIG. 1 enables the center electrode 116
to be isolated from the quantum well 112 by displacing the electrodes in
the horizontal direction. One of the contact electrodes (the p-electrode
116 in FIG. 1) is placed inside the silicon ring. The other electrode is
placed outside the ring, as previously discussed. Both of the electrodes
are located at a distance of approximately 0.3 to 1.0 micrometers from
the silicon ring 105 where the optical mode is guided. This allows a
relatively thin layer of III-V group material to be located on top of the
silicon ring to overlap with the optical mode and to provide the optical
gain necessary to achieve lasing. This thin gain layer does not
significantly affect the ability of the optical mode to bend and remain
confined within micro-ring cavities. Modeling and simulation has shown
that the micro-ring resonator with the structure illustrated in FIG. 1
can have a radius of 2.5 micrometers or less.

[0022]FIG. 2 illustrates a cross sectional view of a simulated optical
mode using the structure illustrated in FIG. 1. A first side of the
silicon micro-ring resonator 105 is shown with the optical mode 202 being
carried substantially within the silicon micro-ring resonator. The actual
size of the optical mode depends on the type of mode that is supported by
the micro-ring resonator and the wavelength of the light within the
resonator. A portion of the optical mode can extend through the n-contact
108 and into the quantum well 112. As previously discussed, the quantum
well may be a single or multiple quantum well configuration. The portion
of the optical mode that extends into the quantum well can be amplified
as the PN junction is forward biased to direct current to flow into the
quantum well and electrically pump the portion of the optical mode that
couples to the quantum well. The light within the quantum well is
amplified and returned to the resonator. The optical mode may be
evanescently coupled to the quantum well.

[0023]FIG. 3 illustrates a top view of the hybrid III-V-silicon micro-ring
electrically pumped laser system 100. The center electrode 116 is shown
at the center of the micro-ring resonator 105. A portion of the n-contact
108 is shown between the center electrode 116 and the outer electrode
110. An optical waveguide 302 can be located near the laser system to
allow the amplified light within the micro-ring resonant to evanescently
couple into the waveguide. In one embodiment, a wrap around waveguide can
be used to increase the amount of light that evanescently couples into
the waveguide from the laser system. The waveguide may be placed at a
distance 306 of less than one third of the wavelength of the light. In
one embodiment, the waveguide may be placed at a distance of 0.200
micrometers (200 nanometers) from the micro-ring resonator 105. The width
304 of the waveguide can be on the order of 0.450 to 0.500 micrometers.
The waveguide can be used to carry light away 308 from the laser
resonator to other portions of an integrated circuit or to nearby chips
or other components on a circuit board.

[0024]The structure of the hybrid III-V-silicon micro-ring electrically
pumped laser system 100 provides several advantages over previous hybrid
laser systems. First, the compact size of the laser enables large-scale
integration of a large number of the laser-on-chip systems without
occupying significant space on the chip. Second, the silicon micro-ring
resonator 105 can be fabricated using industry-standard CMOS-compatible
techniques. Third, the small volume of the micro-ring resonator allows
for low-power, high-speed (>1 GHz) direct modulation of the laser by
applying a modulated signal to the PN junction surrounding the quantum
well. This allows data to be inexpensively transmitted at relatively high
rates, thereby reducing or eliminating bandwidth bottlenecks that occur
in integrated electrical systems. Fourth, the micro-ring resonator 105
provides much larger longitudinal-mode spacing than other hybrid silicon
laser configurations such as the racetrack configuration. The
longitudinal mode spacing is inversely proportional to the micro-ring
resonator length. The larger mode spacing can enable single
longitude-mode lasing, thereby resulting in a much higher quality of the
laser light output from the micro-ring resonator.

[0025]In another embodiment, an additional structure for a hybrid
III-V-silicon micro-ring electrically pumped laser system 400 is
illustrated in FIG. 4. The embodiment illustrated in the cross-sectional
illustration of FIG. 4 includes a substrate 402 coupled to an
under-cladding 404 that is optically coupled to a silicon micro-ring
resonator 405. The under-cladding layer is formed of a material having an
index of refraction that is less than the index of refraction of the
silicon micro-ring resonator and that is substantially optically
transparent at a wavelength of laser light within the micro-ring
resonator. An inside gap 420 and outside gap 406 is shown relative to the
resonator. The inside and outside gaps can be formed of a material having
an index of refraction that is less than the index of refraction of the
silicon micro-ring resonator and that is substantially optically
transparent at a wavelength of laser light within the resonant cavity,
such as air, vacuum, silicon dioxide, silicon nitride, and the like.

[0026]A trapezoidal shaped buffer 414 formed of a III-V group
semiconductor material and doped with a first type of carrier is shown.
The carrier may be either an n-type carrier or a p-type carrier. The
trapezoidal shaped buffer 414 is optically coupled to the quantum well
412. A second buffer 408 formed of III-V group semiconductor material and
doped with a second carrier having a charge opposite the first carrier is
located between a quantum well 412 and the silicon micro-ring resonator
405. The second buffer has a sufficient length to interface with both
sides of the silicon micro-ring resonator.

[0027]The trapezoidal shaped buffer 414 and the second buffer 408 are
configured to form a PN junction, with the quantum well 412 located
between the trapezoidal shaped buffer and the second buffer. The PN
junction supplies carriers to be injected into the quantum well to
provide optical gain to light within the silicon micro-ring resonator
405.

[0028]A ring electrode 410 is electrically coupled to a narrow end of the
trapezoidal shaped buffer 414. The ring electrode may be formed of metal
or another highly conductive material or composite. The wide end of the
trapezoidal shaped buffer is in direct contact with the quantum well 412.
The quantum well, the trapezoidal shaped buffer, and the ring electrode
all form a ring above the silicon micro-ring resonator 405. A center
electrode 416 is placed near a center of the micro-ring resonator and
contacts the second buffer 408 located on top of the resonator. The
location of the center electrode allows carriers to be injected into the
quantum well by applying a bias potential between the center electrode
and the ring electrode.

[0029]The trapezoidal shaped buffer 414 can have a trapezoidal or
triangular shape. The buffer can be formed using, for example, a weakly
anisotropic etching process. In one embodiment, the buffer may be etched
to form a plurality of levels, with each increasing level having a
decreasing length to form a pyramidal shaped buffer.

[0030]FIG. 5 illustrates a cross sectional view of a simulated optical
mode using the structure illustrated in FIG. 4. One side of the silicon
micro-ring resonator 405 is shown with a portion of the optical mode 502
being carried within the silicon micro-ring resonator. The actual size of
the optical mode depends on the type of mode that is supported by the
micro-ring resonator and the wavelength of the light within the
resonator. A portion of the optical mode can extend through the n-contact
408, into the quantum well 412, and into the trapezoidal shaped buffer
414. It should be noted that the trapezoidal shaped buffer can be created
using a plurality of etched steps to form a pyramidal shaped buffer.

[0031]As illustrated in FIG. 5, the system shown in FIG. 4 provides a
significant improvement over the system shown in FIG. 1 in the amount of
the optical mode 502 that is located within the quantum well 412. The
thickness of the micro-ring resonator 405, second buffer 408, and the
quantum well 412, along with the height and shape of the trapezoidal
shaped buffer 414 can enable the area of the optical mode that has the
greatest amount of electromagnetic energy to be positioned within the
quantum well. Constructing the system such that the highest density of
the optical mode is located within the quantum well provides a
significant improvement in the efficiency of the laser. The confinement
factor of the fundamental mode in the quantum well is approximately 35%,
significantly higher than other types of III-V group-silicon hybrid laser
systems. The shape of the structure illustrated in FIG. 5 enables the
optical mode to directly couple with the quantum well 412 and the
trapezoidal shaped buffer 414. The direct optical coupling provides an
optical mode with substantially higher power than can be achieved through
evanescent coupling between the silicon micro-ring resonator 405 and the
quantum well.

[0032]The shape of the trapezoidal buffer 414 can be selected to maximize
the confinement factor of the optical mode. A trapezoidal shaped buffer
with a narrower top will move the fundamental mode downward. Conversely,
a trapezoidal shaped buffer with a wider top will allow the fundamental
mode to be positioned higher within the trapezoidal buffer. Additionally,
the structure illustrated in FIG. 5 provides only a single low-loss mode,
the fundamental transverse-electric mode (TE mode). Because of the shape
of the trapezoidal buffer, a significantly reduced amount of light is
lost at the buffer-electrode transition. Testing has shown that loss with
an aluminum center electrode 410 is approximately 0.4 dB/cm.

[0033]The TE polarization has high optical gain from the quantum well. The
transverse-magnetic (TM) mode and higher order modes have losses that are
two orders of magnitude higher than the fundamental TE-mode. Therefore,
only the fundamental TE-mode will lase. Substantially all of the quantum
well area has effective interaction with the optical mode. Therefore, a
substantial amount of the pump current injected into the quantum well is
used to stimulate photons, thereby resulting in a substantially high pump
efficiency. The confinement factor of the optical mode 502 within the
quantum well 412 can be greater than 35 percent. More typical levels of
confinement can vary from 20 percent to approaching 40 percent.
Stimulated light from the silicon micro-ring resonator illustrated in
FIGS. 4 and 5 can be coupled to a waveguide through evanescent coupling,
as previously discussed and shown in FIG. 3.

[0034]In another embodiment, a method 600 for forming an electrically
pumped laser for stimulating light of a selected wavelength is disclosed,
as shown in FIG. 6. The method includes the operation of forming 610 a
silicon micro-ring resonator on an under-cladding having an index of
refraction that is less than an index of refraction of the silicon
micro-ring resonator. The method further includes the operation of
joining 620 a first buffer layer with the silicon micro-ring resonator.
The first buffer layer is formed of a III-V group semiconductor material
doped with a first type of carrier. An additional operation involves
attaching 630 a quantum well to the first buffer layer, with the quantum
well being optically coupled to the silicon micro-ring resonator.

[0035]The method 600 further involves connecting 640 a second buffer layer
to the quantum well. The second buffer layer can be formed of III-V group
semiconductor material doped with a second type of carrier having a
charge opposite the first type of carrier. The second buffer layer can
have a trapezoidal shape having a wide area coupled to the quantum well
and a narrow area opposite the wide area. The method further includes
joining 650 a ring electrode to the narrow area of the trapezoidal shaped
second buffer layer. An additional operation provides for including 660 a
center electrode about a center of the silicon micro-ring resonator to
enable carriers to be injected into the quantum well between the center
electrode and the ring electrode to provide amplification of the light of
the selected wavelength.

[0036]While the forgoing examples are illustrative of the principles of
the present invention in one or more particular applications, it will be
apparent to those of ordinary skill in the art that numerous
modifications in form, usage and details of implementation can be made
without the exercise of inventive faculty, and without departing from the
principles and concepts of the invention. Accordingly, it is not intended
that the invention be limited, except as by the claims set forth below.